[4.0] check for libxml

[brianteeman]

PR for #29425

This is a real edge case discovered by @Fedik #29425 (comment)

libxml is enabled by default when compiling php and it cannot be disabled etc in a php.ini

The check I have put in place is the same one that myBB uses for the same issue.

The only questions are

1. Did I put the check early enough
2. Do we really need it for such an edge case

[dgrammatiko]

@brianteeman although this would work I think that the check needs to be in the Initial checks (compatibility layer):

joomla-cms/installation/src/Model/ChecksModel.php

Line 66 in 77bcd71

public function getPhpOptions()

Also that would result to a better error view

[HLeithner]

@brianteeman can you fix the cs plz

[Fedik]

maybe better to place it in installation/includes/app.php or even installation/index.php

with some nice message like:

joomla-cms/installation/index.php

Lines 20 to 26 in 77bcd71

	die(
	str_replace(
	array('{{PHP_VERSION}}', '{{BASEPATH}}'),
	array(JOOMLA_MINIMUM_PHP, 'http://' . $_SERVER['SERVER_NAME'] . '/'),
	file_get_contents(dirname(__FILE__) . '/../templates/system/incompatible.html')
	)
	);

I think that the check needs to be in the Initial checks (compatibility layer)

The problem the App does not even start if xml not available ;)

upd: the text in templates/system/incompatible.html can be updated to show more info, than just minimum php version

[dgrammatiko]

maybe better to place it in installation/includes/app.php or even installation/index.php

Since all the checks from the Model could end up being foobar if any of these fail I guess beefing up these files is a more realistic approach. Yeah I know the code will end up being god awful but functional code is better than beautiful non functional code.

My 2c